1. Field of the Invention
The present invention relates to diagnostic imaging inside the human body. In particular, the present invention relates to utilizing multiple capsule cameras.
2. Discussion of the Related Art
Devices for imaging body cavities or passages in vivo are known in the art and include endoscopes and autonomous encapsulated cameras. Endoscopes are flexible or rigid tubes that pass into the body through an orifice or surgical opening, typically into the esophagus via the mouth or into the colon via the rectum. An image is formed at the distal end using a lens and transmitted to the proximal end, outside the body, either by a lens-relay system or by a coherent fiber-optic bundle. A conceptually similar instrument might record an image electronically at the distal end, for example using a CCD or CMOS array, and transfer the image data as an electrical signal to the proximal end through a cable. Endoscopes allow a physician control over the field of view and are well-accepted diagnostic tools. However, they do have a number of limitations, present risks to the patient, are invasive and uncomfortable for the patient, and their cost restricts their application as routine health-screening tools.
Because of the difficulty traversing a convoluted passage, endoscopes cannot reach the majority of the small intestine and special techniques and precautions, that add cost, are required to reach the entirety of the colon. Endoscopic risks include the possible perforation of the bodily organs traversed and complications arising from anesthesia. Moreover, a trade-off must be made between patient pain during the procedure and the health risks and post-procedural down time associated with anesthesia. Endoscopies are necessarily inpatient services that involve a significant amount of time from clinicians and thus are costly.
An alternative in vivo image sensor that addresses many of these problems is capsule endoscope. A camera is housed in a swallowable capsule, along with a radio transmitter for transmitting data, primarily comprising images recorded by the digital camera, to a base-station receiver or transceiver and data recorder outside the body. The capsule may also include a radio receiver for receiving instructions or other data from a base-station transmitter. Instead of radio-frequency transmission, lower-frequency electromagnetic signals may be used. Power may be supplied inductively from an external inductor to an internal inductor within the capsule or from a battery within the capsule.
An early example of a camera in a swallowable capsule is described in U.S. Pat. No. 5,604,531. Other patents, such as U.S. Pat. Nos. 6,709,387 and 6,428,469, describe more details of such a system, using a transmitter to send the camera images to an external receiver. Still other patents, including U.S. Pat. No. 4,278,077, describe similar technologies. For example, U.S. Pat. No. 4,278,077 shows a capsule with a camera for the stomach, which includes film in the camera. U.S. Pat. No. 6,939,292 shows a capsule with a buffering memory, a timer, and a transmitter.
One advantage of an autonomous encapsulated camera with an internal battery is that measurements may be made with the patient ambulatory, out of the hospital, and with moderate restriction of activity. The base station includes an antenna array surrounding the bodily region of interest and this array can be temporarily affixed to the skin or incorporated into a wearable vest. A data recorder is attached to a belt and includes a battery power supply and a data storage medium for saving recorded images and other data for subsequent uploading onto a diagnostic computer system.
A typical procedure consists of an inpatient visit in the morning during which a clinician attaches the base station apparatus to the patient and the patient swallows the capsule. The system records images beginning just prior to swallowing and records images of the gastrointestinal (GI) tract until its battery becomes fully discharged. Peristalsis propels the capsule through the GI tract. The rate of passage depends on the degree of motility. Usually, the small intestine is traversed in 4 to 8 hours. After a prescribed period, the patient returns the data recorder to the clinician who then uploads the data onto a computer for subsequent viewing and analysis. The capsule is passed in time through the rectum and need not be retrieved.
There is also another type of autonomous capsule camera that utilizes on-board data recorder to store captured image data from the camera and other associated data. Therefore such capsule camera does not require a built-in radio transmitter to send data for the captured images. U.S. Pat. No. 6,800,060 describes a swallowable data-recorder capsule that may be retrieved after passing from the body. However, this system specifies an expensive and rare ultra-high-density atomic-resolution storage (ARS) medium. U.S. Pat. No. 7,495,993 describes a semiconductor memory as on-board storage for capsule camera applications. This semiconductor based on-board storage offers several advantages over the ARS storage in terms of lower cost and flexible data access.
The capsule camera allows the GI tract from the esophagus down to the end of the small intestine, especially the small intestine, to be imaged in its entirety, although it is not optimized to detect anomalies in the stomach. Color photographic images are captured so that anomalies can be detected even when only small visually recognizable characteristics, not topography, are available. The procedure is pain-free and requires no anesthesia. Risks associated with the capsule passing through the body are minimal—certainly, the risk of perforation is much reduced relative to endoscopy. The cost of the procedure is also less than for an endoscopy due to the decreased use of clinician time and clinic facilities, and the absence of anesthesia.
A limitation of the current solutions is their inability to reliably image the colon. The colon presents a number of challenges for the imaging system. A number of complications arise because the capsule takes longer to pass through the entire GI tract than just through the small intestine. In fact, ingested material can easily take 24 hours or longer to pass through the colon, although this time can be reduced with motility-enhancing drugs. Therefore to use the capsule camera for imaging the GI tract through colon would thus require extended battery life.
While the technology of capsule camera has advanced over the years, the detection rate of anomalies by a commercially available capsule camera is around 80% as reported in a recent study. Accordingly, it is desirable to further improve the detection rate. On the other hand, the passage rate for a swallowable camera is about 4 to 8 hours in the small intestines and it may take 24 hours or longer for the camera to go through the colon. Therefore, it is desirable to provide a capsule camera apparatus with extended imaging time so that it may reliably be used for imaging the GI tract through colon. This need is the same for the type of autonomous capsule camera using radio transmitter to send the captured images, as well as the type of autonomous capsule camera using on-board memory for images recorded by the digital camera.